About the Caesar Cipher
A Caesar shift substitution cipher is a simple cipher where every letter of the
alphabet is substituted by another.
To start with, each letter of the alphabet is replaced by a number.
Then we apply a shift, say 3, to the entire list by adding 3 to each number in turn. So,
| A||→|| 0 + 3 = 3|
| B||→|| 1 + 3 = 4|
| C||→|| 2 + 3 = 5|
| Z||→|| 25 + 3 = 28|
Finally the number is replaced with the letter that corresponds to the letter from the initial list.
|i.e.||A→ 0→ 3→ D||B→ 1→ 4→ E||C→ 2→
5→ F||... etc.|
You will notice that with the letters X, Y and Z we have a problem here because no letters are assigned to 26, 27 and 28.
This problem is resolved by using modular arithmetic, in this case we are using mod 26 [more].
|So,||X→ 23→ 26→ 0→
A||Y→ 24→ 27→ 1→ B||and||Z→ 25→ 28→ 2→ C.|
The following table shows the complete alphabet after a Caesar shift of three places. Click on the buttons below to modify
the table for any shift.
Creating a Caesar shift cipher
- The Caesar shift wheel. [more]
Deciphering a Caesar shift cipher
- Using the Vigenere square. [more]
- Using frequency analysis. [more]
Caesar shift cipher encipher/decipher tool. [more]